There are many superlatives to heap on the M340i’s performance and there’s not enough air here in Denver for all the breathless hyperbole I have for it. This year, the M340i’s turbo-6 gets massaged up to 382 horsepower (up from 355 hp last year) and it can spring from 0-60 mph in 4.1 seconds. Carved into the automotive Mount Rushmore in my mind is the BMW B58 engine, a superhero under hoods that’s excellent in every application. Its power and turbos build quickly but surge at 4,000 rpm. The revs race past 6,000 rpm in a blink